Digital display devices and other digital peripheral devices are well known in the art. Digital display devices can be designed with video signal inputs to accept either a direct digital signal and/or an analog signal which is converted to digital by the display device. Additionally, some analog display devices accept a digital video signal output.
One concern in the industry is the unauthorized of copying of copyrighted content which may be contained in a video signal. If a video signal is intercepted between transmission from a computer system to a peripheral device, such as a display, it can be used to make virtually identical copies of the video content without any degradation or loss of quality.
Some systems avoid this concern by having an analog output from the computer and an analog input to the digital display device so that only an analog signal may be intercepted. Although copies of the video content can be made based upon the analog signal, there is inherently some degradation and quality loss associated with such an analog signal which compounds when repeated copies are made using analog transmissions. However, where an analog signal is transmitted from the computer to the peripheral digital device, the signal received by the digital device is likely to be of a lower quality than if a digital signal were transmitted between the computer and the peripheral device.
In order to facilitate the transmission of digital signals from a computer to a digital peripheral device while inhibiting unauthorized content copying, encryption schemes and protocols have been developed to encrypt the digital signal before transmission from the computer and then to decrypt the signal in the digital peripheral device. One proposed protocol is High bandwidth Digital Content Protection (HDCP) specification which requires a graphics controller to store a large set of encryption keys that are unique to the interface devices used to output an encrypted digital signal. Under HDCP, each interface device must be allocated its own unique encryption key data. Thus, each interface device or computer system must be individualized. This poses a manufacturing problem since it is more efficient to manufacture on a mass scale computer systems and/or interface cards which are identical.
It would be desirable to provide a computer system and/or interface device which can be easily mass produced, but which also can support encryption systems such as HDCP.